1. Field of the Invention
The invention relates to systems and methods for advancing tape media cartridges in an automated tape library. Specifically, the invention relates to apparatus, systems and methods for generating a spring force to advance tape cartridges in a deep slot cell, where the spring force increases in accordance with the number of tape cartridges in the cell.
2. Description of the Related Art
Automated tape libraries (“ATLs”) provide high capacity data storage at low cost, with current ATLs equipped to provide about ten thousand times the capacity of a typical hard drive. As a result, ATLs are used extensively as enabling hardware in backup and recovery systems.
In operation, ATLs utilize physical tape drives to read and write data to tape media cartridges for storage. Tape media cartridge slots hold the tape media cartridges inside the ATL, and a robotic mechanism, or “picker,” moves tape media cartridges between their slot and another location as needed. For example, the picker may transport a particular tape media cartridge to the tape drive, another slot, or a cartridge access port for import or export from the library.
Recent advances in automated tape library technology include deep slot cells that are able to hold multiple tape media cartridges at a time. Such deep slot cells provide increased storage density, thereby facilitating increased data storage capacity. In use, tape media cartridges in a deep slot cell must be advanced to a frontmost position in the cell to enable the picker to access and transport the cartridge.
One method for advancing tape media cartridges in a deep slot cell uses a flat sheet spring to apply a substantially constant force on the tape media cartridges in the cell. While this method succeeds in pushing tape media cartridges forward with only a nominal impact on storage density, it does not account for the variation in frictional load that results when a tape media cartridge is removed.
Indeed, the major force that must be overcome to advance cartridges from the back of the cell to the front of the cell is friction resulting from the interaction of the cartridge with the cell. Each individual cartridge contributes to the total frictional load. Accordingly, the force needed to overcome friction varies with the number of cartridges in the cell.
A flat sheet spring exerts a substantially constant spring force. The force is appropriate when the cell contains the maximum number of cartridges, but excessive when one or more of the cartridges is removed. This may result in remaining cartridges being forced through a cartridge retention mechanism designed to retain cartridges in the cell. Further, flat sheet springs tend to exhibit less wearability and a shorter life than other push mechanisms due to imperfections in the sheet material. A sheet spring is typically only about 0.1 mm (0.004 inches) thick. Accordingly, even small defects may occupy a significant portion of the cross-section of the spring, causing a life-shortening effect.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system and method that generates a spring force to advance cartridges forward, where the spring force increases in accordance with a number of cartridges in the deep slot cell. Beneficially, such an apparatus would provide increased reliability and component longevity while promoting storage density and cost efficiencies. Such an apparatus, system and method are disclosed and claimed herein.